Association between preoperative fasting time and clinical outcomes in surgical patients in a private general hospital

ABSTRACT Purpose: Surgical patients are routinely subjected to long periods of fasting, a practice that can exacerbate the metabolic response to trauma and impair postoperative recovery. The aim of this study was to evaluate the association between preoperative fasting time and clinical outcomes in surgical patients. Methods: An observational, prospective study with a non-probabilistic sample that included patients of both sexes, aged over 18, undergoing elective surgeries. Data were extracted from electronic medical records, and a questionnaire was applied in 48 hours after surgery. Variables related to postoperative discomfort were assessed using an 11-point numeric rating scale. Results: The sample consisted of 372 patients, and the duration of the surgical event ranged from 30–680 minutes. The incidence of nausea (26.34%) was twice that of vomiting (13.17%) and showed an association with the surgical procedure’s size (p = 0.018). A statistically significant difference was observed only between pain intensity and preoperative fasting times for liquids (p = 0.007) and postoperative fasting time (p = 0.08). The occurrence of postoperative complications showed no association with preoperative fasting time (p = 0.850). Conclusions: Although no association was observed between preoperative fasting time and surgical complications, it is noteworthy that both recommended and actual fasting time exceeded the proposed on clinical guidelines.


Introduction
The practice of preoperative fasting gained prominence in the mid-20th century following a study published by Mendelson  (1946), which recommended fasting as a measure to prevent post-anesthetic respiratory complications resulting from the aspiration of gastric contents into the lungs 1,2 .The change from this fasting pattern to current guidelines was initially proposed in 1999 by the American Society of Anesthesiologists (ASA) 3 .
In Brazil, inspired by fast-track protocols from the 1980s and Enhanced Recovery After Surgery (ERAS), the Acceleration of Total Postoperative Recovery (ACERTO) project, originally conceived as a research project, was implemented in 2005 in the surgical ward of the Júlio Muller University Hospital (Cuiabá, MT, Brazil), following a six-month audit.Based on evidence-based practice, since its inception, ACERTO has expanded the vision of perioperative care by implementing new multimodal conducts to different surgical specialties, clinical profiles, and surgical sizes 4 .
Prolonged preoperative fasting is a harmful and unnecessary process for most patients, which can exacerbate the cascade of the metabolic response to trauma, worsen insulin resistance and protein catabolism, and alter gastrointestinal function 5 .
The ASA risk score is a classification of the patient's physical status, categorizing them based on their overall clinical condition and the presence or absence of systemic disease 15 .In addition to surgical size reported in the medical records by the surgical team, surgeries were categorized into two sizes, according to duration: minor, for surgeries with the duration of 4 hours or less, and major, for surgeries lasting more than 4 hours 16 .
Patients were followed in a hospital setting for a period of 90 days, and the following variables were also considered: mortality, frequency of hospital readmission, frequency of surgical re-intervention, and occurrence of perioperative complications (aspiration, wound dehiscence, evisceration, abscess or wall collection, active bleeding from surgical wound, suture or anastomosis dehiscence and fistula, cavitary abscess or collection, inadvertent injury to structure(s), cavitary bleeding, surgical site infection, and prolonged ileus).

Data collection
Data collection was conducted in 48 hours after the surgical event by applying a questionnaire to the patient.The questionnaire aimed to collect information about the time of pre-procedure hospitalization, preoperative fasting guidance and recommended time, actual preoperative fasting time, postoperative fasting time until resumption of oral or enteral feeding, and postoperative discomfort.
Preoperative fasting time was calculated based on the time of the last intake of solids and liquids and the time of anesthetic induction.Postoperative fasting time was considered the time difference between the end of surgery and the introduction of oral or enteral feeding.Total fasting time was defined as the time elapsed between the time of the last intake of solids and the introduction of oral or enteral feeding after surgery.
Variables related to postoperative discomfort, such as pain, hunger, and thirst, were assessed using an 11-point numeric rating scale (NRS) (0 = absence of symptom; 10 = extreme symptom), and nausea/vomiting were assessed based on occurrence and number of episodes.The NRS is a unidimensional instrument that classifies symptom intensity based on self-report by individuals.It is a simple, quick, easily applicable, and cost-effective tool validated for various types of patient and has demonstrated good performance for pain intensity assessment.Scores are interpreted as: 0 = absence of symptoms, 1-3 = mild symptoms, 4-6 = moderate symptoms, and 7-10 = intense symptoms 17,18 .

Statistical analysis
All statistical analyses were performed using the Statistical Package for the Social Sciences software, version 22 for Windows (SPSS, Inc., Chicago, IL, United States of America).Data distribution and adherence to the normal curve were verified using the Kolmogorov-Smirnov Test.Continuous variables were described using means and their respective standard deviations, while non-parametric variables were described using medians and interquartile range (IQR), as appropriate.. Categorical variables were expressed as absolute numbers and relative frequencies.Data distribution and adherence to the normal curve were verified using the Kolmogorov-Smirnov's test, and non-parametric tests were adopted based on the results.Associations between categorical variables were tested using the χ 2 test.For the comparison of numerical variables between two groups with independent samples, the Mann-Whitney's test was used, while for comparisons among three or more groups the Kruskal-Wallis' test was applied.The Dunn multiple comparisons test was used to identify differences between subgroups.The level of statistical significance was set at 5% (p < 0.05).

Results
The sample consisted of 372 patients, with 59.14% (n = 220) being female and mean age of 52.40 ± 17.23 (18-95).One hundred and six patients (28.49%) were transferred to the intensive care unit (ICU) immediately postoperatively, with a median length of stay in this unit of two days (IQR = 1;2).General anesthesia was the anesthetic technique used in 69.95% (n = 256) of the surgeries.Forty-four patients (49.44%) had an ASA risk score of I, and 75% (n = 147) underwent major surgeries.The duration of the surgical event ranged from 30 to 680 minutes, with 52.42% (n = 195) of the surgeries performed in 120 minutes (Table 1).Oncological surgeries were the most common (30.91%), followed by gastrointestinal (16.57%) and plastic surgeries (15.32%) (Table 2).
The preoperative fasting time for solids ranged from 5 hours and 50 minutes to 65 hours and 10 minutes, with 64.25% (n = 239) of patients abstaining from solid food for 12 hours or more.Almost 45% (n = 166) did not consume liquids for an equal period, 39.52% (n=146) had their diet resumed in 4 hours after the surgical event, and 40.34% (n = 150) underwent total fasting for 24 hours or more.The medians for the actual preoperative fasting time for solids and liquids, postoperative fasting time, and total fasting time were 13.54 (IQR = 11-17) hours, 11.37 (IQR = 9.33-14.67)hours, 4.67 (IQR = 3.17-12.85)hours, and 22 (IQR = 17.62-29) hours, respectively.Abdominal surgeries had a higher median fasting time for solids, 15.25 (IQR = 13-17.94)hours.Oncological surgeries had a shorter fasting time for liquids, 9.42 (IQR = 8.38-14.79)hours.Only in cardiac and vascular surgeries 100% of the patients received a diet in 24 hours postoperatively.Thirst had the highest score among the three variables analyzed using the NRS, with a median of 6 (IQR = 3-9) points, as shown in Fig. 1.Nausea was reported by 26.34% (n = 98) of participants, and vomiting by 13.17% (n = 49).Patients who experienced longer preoperative fasting times for solids and liquids reported intense pain, while those with longer times for diet reintroduction postoperatively mentioned moderate pain (Table 3).There was a statistically significant difference only between pain intensity and preoperative fasting times for liquids (p = 0.007) and diet reintroduction time postoperatively (p = 0.08).Preoperative fasting time for liquids and time for diet reintroduction were longer among patients reporting intense pain (p = 0.005) and moderate pain (p = 0.004), respectively.The results indicated that the surgical size (minor or major according to time) influenced the occurrence of nausea (p = 0.023); a major surgery was associated with a higher incidence of this symptom.However, no such correlation was observed between surgical size and the occurrence of vomiting (Table 4).
There was no association between the occurrence of nausea and perioperative fasting times, neither between the occurrence of vomiting and preoperative fasting times for solids and liquids.However, it was observed that the time for diet reintroduction postoperatively (p = 0.021) and the total fasting time (p = 0.002) were significantly longer in the group of patients who reported postoperative vomiting episodes.Among the adverse events in 90 days and perioperative complications, there were cases of surgical wound infection (n = 6), fistulas (n = 4), wall abscess (n = 3), prolonged ileus (n = 1), suture dehiscence (n = 1), cavitary collection (n = 1), as well as the need for hospital readmission (n = 13) and surgical re-intervention (n = 9).There was no record of pulmonary aspiration, but one patient experienced mortality.The occurrence of postoperative complications showed no association with preoperative fasting time (p = 0.850).
In a multicenter cohort study with 924 patients, Beck et al. 20 observed an average preoperative fasting duration of 17.02 ± 6.54 hours for solid foods and 9.21 ± 5.48 hours for liquids, nearly five times longer than recommended by guidelines.Solid food reintroduction occurred after 9.42 ± 12 hours after surgery, and the mean perioperative fasting time for solids was 28.23 ± 14.02 hours 20 .Zhu et al. 21found that patients undergoing elective surgeries at a tertiary hospital also had a high average fasting time for solids, 13.41 ± 2.64 (7-20) hours, and for liquids, 10.27 ± 3.67 (1.5-18) hours.
Diet reintroduction occurred in 24 hours of surgery in 91.67% of cases, following recommendations of starting a diet in the first 24 hours postoperatively, provided the patient is hemodynamically stable 9 .Early postoperative nutrition is not only safe, but also reduces the risk of anastomosis dehiscence, lowers postoperative complications, shortens hospital stays, reduces hospital costs, and decreases morbidity and mortality 9,22,23 .Dehydration, hypoglycemia, a higher incidence of postoperative nausea and vomiting, and increased patient discomfort (e.g., hunger, thirst, fatigue, and anxiety) are some of the negative physiological effects associated with prolonged fasting 24,25 .Regarding the intensity of postoperative discomfort symptoms, there was mild pain (3; IQR = 0-6 points), moderate thirst (6; IQR = 3-9 points), and moderate hunger (6; IQR = 0-6 points).No thirst, hunger and pain were reported by 8.9, 17.7, and 27.2% of patients, respectively.Gul et al. 25 analyzed the relation between traditional fasting policies and preoperative discomfort.About 80% of patients reported no thirst or hunger on the night before surgery, but symptoms intensified with prolonged fasting.On the day of surgery, 43.3% of participants felt some degree of hunger or thirst, 46.4% reported mild to intense weakness, and 39.6% discomfort.Furthermore, preoperative fasting time for solids was associated with thirst, hunger, dry mouth, and weakness, while total fluid fasting time was associated with hunger and dry mouth.
A meta-analysis involving 5,606 patients from 57 that aimed evaluate the effect and safety carbohydrate intake in the preoperative period of adult patients observed that this practice reduces discomfort, including dry mouth, thirst, hunger, and pain; reduces hospitalization time; and decreases insulin resistance when compared to fasting.Given the benefits, safety, and low cost of offering carbohydrates preoperatively, the authors suggested that this strategy should be adopted by surgeons and anesthesiologists to improve surgical recovery 26 .
Pain is reported as the primary complication in the postoperative period.In this study, the preoperative fasting time for liquids and the postoperative fasting time were longer among patients who reported intense pain (p = 0.005) and moderate pain (p = 0.004), respectively.Torabikhah et al. 27 , when investigating the impact of reducing the preoperative fasting time on postoperative pain in orthopedic patients, found that the pain intensity in the group with shortened fasting was lower than that in the control group, but without statistical significance.The authors considered that the subjectivity of the concept of pain and the lack of a more precise tool for measuring this symptom may have influenced the results.It is likely that a shorter fasting time allows patients to be more relaxed and have a lower perception of pain, minimizing discomfort 28 .
Nausea and vomiting are undesirable, but preventable effects that lead to dissatisfaction and complications such as dehydration, electrolyte imbalance, wound dehiscence, and delays in hospital discharge 29 .The overall incidence of postoperative nausea and vomiting (PONV) is 50 and 30%, respectively 30 , higher than the findings in this study, in which 26.34% of patients reported nausea and 13.17% reported vomiting.Marquini et al. 31 randomized 80 women undergoing gynecological surgeries into two groups (control group: 200 mL of inert solution; intervention group: 200 mL of a clear supplement 4 hours before the procedure) to assess the effects of preoperative fasting abbreviation on the incidence of PONV.The incidence of nausea and vomiting was also lower than described in the literature, with 18.9% in the control group and 10.8% in the intervention group, but there was no statistically significant difference between the groups.Among the independent risk factors for developing PONV are female gender, history of postoperative nausea and vomiting or motion sickness, non-smoking status, and postoperative opioid use [29][30][31] .The association between the type of surgery and PONV is still not well defined, but it is believed that longer surgeries favor its occurrence due to prolonged exposure to general anesthesia and high-dose opioid administration.PONV prophylaxis is indicated for all surgical patients and involves reducing preoperative fasting time, multimodal analgesia strategies, conscious fluid use, and antiemetic use for patients at medium or high risk 32,33 .
Xu et al. 34 revealed through a meta-analysis that reducing preoperative fasting time for patients undergoing laparoscopic cholecystectomy increases postoperative comfort by reducing the incidence of nausea and vomiting, improving insulin resistance, and minimizing the stress response.A study with patients undergoing elective colorectal surgeries using measures proposed by the ACERTO protocol analyzed risk factors associated with various clinical outcomes and demonstrated, through univariate analysis, that prolonged preoperative fasting time (greater than 4 hours) increased the risk of surgical site infection by more than five times, anastomotic fistula by 9.27 times, pneumonia-atelectasis by 10 times, and death by 20 times 35 .
In the present study, 6.18% of patients had postoperative complications.Although high, the preoperative fasting duration (13.54;IQR = 11; 17 hours) evidenced no association with postoperative complications (p = 0.850).The sample size may have hindered the accurate statistical assessment of the association between fasting time and the occurrence of postoperative complications, a situation attributed to type II error.Lucchesi and Gadelha 36 identified surgical wound infection (27.2%) and surgical re-intervention (18.2%) as the most frequent complications and emphasized that there was no significant difference between nutritional status or perioperative fasting time and the observed complications 36 .Virgens et al. 37 found, in a sample of gastric and colorectal cancer surgical patients, that prolonged perioperative fasting time (59.0 ± 2.4 hours) was an independent predictor of length of stay, but it was not associated with the incidence of postoperative complications and death.

Figure 1 -
Figure 1 -Description of the intensity of variables related to discomfort (thirst, hunger, and pain) assessed using an 11-point numeric rating scale in patients undergoing elective surgeries (n = 372).

Table 1 -
Description of sociodemographic data, perioperative routine, and characteristics of elective surgeries performed at a tertiary hospital.
¥Data with incomplete records in the analyzed medical records; LHS: length of hospital stay; IQR: interquartile range; *surgical size described in the medical records; **surgical size defined according to duration of the procedure; ASA: American Society of Anesthesiologists.Source: Elaborated by the authors.

Table 2 -
Distribution types of elective surgeries performed at a tertiary hospital./type of diet offered in the first postoperative meal, 36.83%(n = 137) received a soft diet, 16.13% (n = 60) received a clear liquids diet, and 2.96% (n = 12) received a diet by enteral route.During hospitalization, two patients received parenteral nutrition due to postoperative complications.
*Maxillary and ophthalmological.Source: Elaborated by the authors.consistency

Table 3 -
Comparison between preoperative fasting time for solids and liquids, diet reintroduction time, and total perioperative fasting time in hours, and the intensity of pain in patients undergoing elective surgeries ! .
!Results: median (interquartile range) in hours.Data was compared by the Kruskal-Wallis' test; *p < 0.05; a,b medians followed by the same letter do not differ, distinct letters indicate statistical difference at the 5% significance level.Source: Elaborated by the authors.

Table 4 -
Association between surgical size and the occurrence of postoperative nausea and vomiting in patients undergoing elective surgeries*.Data compared using the χ 2 test.Source: Elaborated by the authors. *